U.S. Tornado Climatology

Because a tornado is part of a severe convective storm, and these storms occur all over the Earth, tornadoes are not limited to any specific geographic location. In fact, tornadoes have been documented in every state of the United States, and on every continent, with the exception of Antarctica (even there, a tornado occurrence is not impossible). In fact, wherever the atmospheric conditions are exactly right, the occurrence of a tornadic storm is possible. See NOAA's National Severe Storms Laboratory (NSSL) Severe Weather 101 information for more on the conditions necessary for tornado formation.

However, some parts of the world are much more prone to tornadoes than others. Globally, the middle latitudes, between about 30° and 50° North or South, provide the most favorable environment for tornadogenesis. This is the region where cold, polar air meets against warmer, subtropical air, often generating convective precipitation along the collision boundaries. In addition, air in the midlatitudes often flows at different speeds and directions at different levels of the troposphere, facilitating the development of rotation within a storm cell. Interestingly, the places that receive the most frequent tornadoes are also considered the most fertile agricultural zones of the world. This is due in part to the high number of convective storms delivering needed precipitation to these areas. Simply because of the large number of convective storms and the favorable environment, the odds are increased that some of these storms will produce tornadoes.

In terms of absolute tornado counts, the United States leads the list, with an average of over 1,000 tornadoes recorded each year. Canada is a distant second, with around 100 per year. Other locations that experience frequent tornado occurrences include northern Europe, western Asia, Bangladesh, Japan, Australia, New Zealand, China, South Africa, and Argentina. In fact, the United Kingdom has more tornadoes, relative to its land area, than any other country. Fortunately, most UK tornadoes are relatively weak.